1. Field of the Invention
The present invention relates to an abrasive tool with metal binder phase, containing electrodeposited abrasive tool or metal bonded abrasive tool, used for the conditioner for carrying out conditioning of the polishing pad. Which is used for the polishing of the surface of workpiece, for example, a semiconductor wafer with CMP equipment etc.
This specification based on the following Japanese Patent applications (Patent Application number No. 11-247676 (JP), No. 11-247677 (JP), No. 11-269298 (JP), No. 11-338734 (JP), No. 2000-29614 (JP), and the written contents of these concerned Japanese applications are taken in as a part of this specification.
2. Background Art
Conventionally, there is CMP equipment (Chemical-Mechanical Polishing machine) which chemically and mechanically polishes the surface of the semiconductor wafer (henceforth a wafer) cut down from the silicone ingot, and shown in FIG. 32 as an example.
It is required that a mirror polish is carried out so that a wafer may serve as high precision and the zero defect surface in connection with microfabrication of devices. The mechanism of polish by CMP is based on the mechano-chemical polishing method, compounded with the mechanical element by particle silica etc. (free abrasive grain) and the etching element by alkali liquid, acid liquid, etc.
The polishing pad 4, which was attached in the main axis 2 as shown in FIG. 33, and consists, for example, of hard urethane is formed on the disk shaped rotation table 3 at this CMP equipment 1. And wafer carrier 5, which can rotate on its axis, is laid out and attached, oppositely to this pad 4, and also in a position eccentric from the main axis 2 of a pad 4. This wafer carrier 5 is made into smaller disk form rather than the pad 4, and holds a wafer 6. And this wafer 6 is arranged between the wafer carrier 5 and the pad 4, and a mirror polish is offered and carried out to polishing the surface by the side of a pad 4.
Many fine foamed layers are prepared on the pad 4, which polishes the wafer 6 and made of hard urethane etc., for the hold of slurry s. Thereby, polish of the wafer 6 is performed by slurry s held in these foamed layers. Then, the problem arises that the polish accuracy and polish efficiency of wafer 6 falls, because the flatness of the polishing surface of the pad 4 falls or clogging occurs by repeating polish of wafer 6.
Therefore, conventionally, as shown in FIG. 32, the pad conditioner 8 is formed in the CMP equipment 1 and used for re-polish or re-grinding (conditioning) of the surface of a pad 4.
An electrodeposited abrasive wheel 11 is attached to this pad conditioner 8, attached through an arm 10 to the rotation axis 9, which is formed in the exterior of the rotation table 3. By making the arm 10 move around the rotation axis 9, both-way rocking of the electrodeposited abrasive wheel 11 is carried out on the rotating pad 4. Thus, the surface of pad 4 is ground, the flatness of the surface of pad 4 is recovered or maintained, and clogging is canceled. Or it can be ground by the wafer career 5 equipped with an electrodeposited abrasive wheel 11.
As shown in FIGS. 33(A) and (B), as for this electrodeposited abrasive wheel 11, at the upper surface of this wheel, a plane and ring-like abrasive grain layer 13 is formed by fixed width on the disk-formed base metal 12. As shown for example, in FIG. 34, this abrasive grain layer 13 is constituted of ultra abrasive grains 14 on the base metal 12, such as a diamond and cBN, distributed and fixed by the electrodeposited metal phase 15 by electroplating etc. This electrodeposited metal phase 15 consists of nickel etc.
In addition, the concave groove 17 is formed in the surface of the abrasive grain layer 13 in the direction of diameter at intervals of predetermined, such as 45 degrees, then slurry s and ground wastes will be discharged outside through this concave groove 17.
By the way, when pad 4 is ground using such an electrodeposited abrasive wheel 11, the electrodeposited abrasive wheel 11 should be carried out both-way rocking on pad 4, covering the distance equivalent to the radius of pad 4 at least. Nap raising of pad 4 is beaten and cut, while the ultra abrasive grains 14, distributed on the abrasive grain layer 13, carries out grinding. The ultra abrasive grains 14 are protruded from the surface of the abrasive grain layer 13, which performs as grinding surface, only about ⅓ of the mean particle diameter of the ultra abrasive grains 14 in this case. Then, the whole surface of the abrasive-grain layers 13 contact directly to workpiece. For this reason, the abutment pressure disperses and becomes slippery, and nap raising could not be cut and pushed down. Then the fault arises that sharpness becomes worse and clogging becomes easy to occur.
Moreover, the other electrodeposited abrasive wheel is disclosed in the Japanese Patent Laid-Open No., 9-19868 for example.
This electrodeposited abrasive wheel gathers 2-10 ultra abrasive grains, and laid out these grains in the shape of islands. These islands-like ultra abrasive grains are distributed on the surface of the abrasive grain layer, which corresponds to a grinding surface, in order to prevent clogging at the time of grinding, and also to continue grinding for a long period of time. In such an electrodeposited abrasive wheel, masking on a base metal is provided, then island-like priming plating is formed at first. Then, temporary fixation against 2-10 ultra abrasive grains for one-layer is carried out by electroplating at this priming plating part. After that, electroplating of the whole base metal is carried out, and ultra abrasive grains are electrodeposited to an abrasive grain layer.
However, in such an electrodeposited abrasive wheel, ultra abrasive grains are electrodeposited and fixed on a flat base-metal surface. Therefore, the difference of the height between the electrodeposited-metal-phase surface of the abrasive grain layer, and the ultra abrasive grains protruded from this surface, is only less than about xc2xd of the mean particle diameter of ultra abrasive grains substantially.
Therefore, when this electrodeposited abrasive wheel is used as a pad conditioner. And if grinding work piece has a composition with much elasticity or flexibility as like the pad 4 of CMP equipment 1, which consists of elastic nap raising 1.7 mm in thickness with foamed layer and an under laid cushion layer with a thickness of about 3.5 mm. The whole abrasive-grain-layer surface will make direct contact with grinding workpiece in this case, since the height difference is less than about xc2xd of the mean particle diameter of ultra abrasive grains. Then, the abutment pressure disperses from ultra abrasive grains and becomes slippery, and nap raising could not be cut and fallen down. Therefore, sharpness becomes worse, and the opening of a foamed layer is crushed, then discharge of ground wastes becomes insufficient. Consequently, there arises a fault that a pad 4 becomes easy to cause clogging.
Moreover, because the height difference (gap) between the ultra abrasive grains at the abrasive grain layer and the surface of the electrodeposited metal phase is small, the grinding liquid (for example, pure water) of pad 4 is flipped out.
Therefore, pad 4 becomes easy to dry and appears a fault that wet grinding becomes spoiled.
In the view of such circumstances mentioned above, the object of the present invention is to provide an abrasive tool with metal binder phase, such as an electrodeposited abrasive tool, having sufficient sharpness and good discharge performance to ground wastes.
Moreover, the other object of the present invention is to provide an abrasive tool, above-mentioned, which provides clean cut end of the opening of the foamed layer of polishing pad, does not occur clogging, and enables to hold slurry in foamed layer.
The other additional object of the present invention is to suppress vibration at the time of grinding.
The other additional object of the present invention is to suppress the solidification of various grinding wastes and slurry s, retained and staid between ultra abrasive grains, and to enable effective discharge.
The other additional object of the present invention is to improve stability at the time of grinding, and to suppress the fall of the sharpness by clogging etc.
The other additional object of the present invention is to suppress the generation of the deficit or crush, etc. at the sharp portion of ultra abrasive grains.
According to the present invention, one aspect of the abrasive tool with metal binder phase, such as electrodeposited abrasive tool, is characterized by several protruded parts formed in a base metal, and several small abrasive-grain-layer parts, laid out at intervals, to which ultra abrasive grains are adhered with metal binder phase on these protruded parts.
If protruded parts are formed at a planate base metal by electroplating etc. the adhesiveness with a base metal becomes worse, then it arises a fault that flaking is easy to occur. Also, the discrepancy arises, that the protrusions tend to blunt or rises appear at peripheral part by masking. On the other hand, according to the present invention, since the strength of protruded parts is high, flaking or bluntness or rises at peripheral part does not appear.
Moreover, the small abrasive-grain-layer part may be equipped with plural ultra abrasive grains, respectively.
The height difference between the ultra abrasive grains in small abrasive-grain-layer parts and bottom part of the abrasive-grain-layer among small abrasive-grain-layer parts is large, because the ultra abrasive grains are formed in small abrasive-grain-layer parts. And even if the grinding work piece was comparatively elastic, such as pad etc. in CMP equipment, it does not show whole surface contact. And the ultra abrasive grains at small abrasive-grain-layer parts contact and carry out grinding against grinding work piece. Then high grinding pressure can be maintained at ultra abrasive grains, and sharpness is improved. And also, grinding liquid can be held at the bottom of abrasive-grain-layer among the small abrasive-grain-layer parts. Then the discharge of ground wastes is improved and ground wastes do not bring out clogging at the portion of ultra abrasive grains.
Also, it would be possible to make the height from the bottom of abrasive-grain-layer among the neighboring small abrasive-grain-layer parts, larger than the mean particle diameter of ultra abrasive grains at small abrasive-grain-layer parts.
The gap between small abrasive-grain-layer parts at an abrasive grain layer and the bottom of an abrasive-grain-layer, can make larger than the mean particle diameter of ultra abrasive grains, and can be obtained at large value.
Then, without occurring whole surface contact, high abutment pressure can be maintained at the ultra abrasive grains of small abrasive-grain-layer parts, sharpness is also improved. And grinding liquid etc. can be held at the bottom part of abrasive-grain-layer, the discharge performance of a ground wastes is improved, then ground wastes do not bring out clogging at the portion of ultra abrasive grains.
Also, it is possible to form the protruded parts, mostly in the columnar shape with a corner R part and the top part, and ultra abrasive grains can be attached at these corners R part and the top part. At the time of grinding, the ultra abrasive grains at corner R part perform rough grinding, and subsequently, ultra abrasive grains at the top can perform finish grinding.
Also, it is possible, to prepare 11-500 pieces of super abrasive grains at each small abrasive-grain-layer part, and the rate of areas, accounted by plane projection, of the ultra abrasive grains against the whole surface area of abrasive grain layer, may be set in the range of 20%-80%.
If there are few ultra abrasive grains less than 11 pieces, rough grinding and finish grinding to pad 4 cannot be performed continuously, and if there are ultra abrasive grains more than 500 pieces, a fault arises that clogging is easy to occur at the ultra abrasive grains. And if the area of ultra abrasive grains is less than 20%, the possibility arises that those ultra abrasive grains may drop out, at the time of grinding. Then, tool life may be shortened, and ultra abrasive grains may stick to grinding work piece, such as polishing pad, and causes damaging of the pad. And if, the area of ultra abrasive grains exceeds 80%, there is a possibility that an electrodeposited abrasive tool may cause clogging.
Also, it is possible, to layout the small abrasive-grain-layer parts at the central domain except for the peripheral domain of the surface of an abrasive grain layer. Then the rocking of the abrasive tool performs grind machining.
Also, it is possible, to arrange the small abrasive-grain-layer parts at the periphery domain except for the central domain of the surface of an abrasive grain layer. In this case, when rotating the abrasive tool and carrying out grind machining, it can perform efficient grind machining by arranging ultra abrasive grains except for the central domain with small peripheral velocity.
Moreover, according to the other aspect of the present invention, the abrasive grain layer is equipped with a central domain and a peripheral domain, and at the central domain, plural above-mentioned small abrasive-grain-layer parts are formed and set at intervals mutually. And plural ultra abrasive grains are attached to these small abrasive-grain-layer parts by the metal binder phase, respectively. And also, ultra abrasive grains are attached to peripheral domain by the metal binder phase. And the concentration of the ultra abrasive grains at peripheral domain is higher than the central domain.
In this case, at the time of grinding, the grinding surface of the electrodeposited abrasive tool has a peripheral domain with higher concentration of ultra abrasive grains than a central domain. So, the grinding surface contacts to grinding work piece stably by the abrasive grain layer at peripheral domain.
Therefore, plane balance are improved, and the vibration can be suppressed at the time of grinding. Moreover, high abutment pressure can be obtained at the ultra abrasive grain of the small abrasive-grain-layer parts within central domain. Then, while grind machining, cut can be performed cleanly. Moreover, by preparing the ultra abrasive grains at the small abrasive-grain-layer part, the height difference between the bottom of abrasive-grain-layer among the neighboring small abrasive-grain-layer parts and small abrasive-grain-layer parts can be made large. And whole surface contact does not occur, even if it for the comparatively elastic grinding work piece, such as the pad of CMP equipment etc. The ultra abrasive grains at small abrasive-grain-layer parts contact to a polishing work piece and carry out grinding, then high abutment pressure can be maintained and sharpness is maintained.
In addition, the ultra abrasive grains at peripheral domain may be individually distributed in the metal binder phase. Or plural small abrasive-grain-layer parts may be constituted like a central domain, and the small abrasive-grain-layer parts may be laid out at smaller mutual intervals than central domain.
Furthermore, the interval may be made the same as that of a central domain, and make the numbers of ultra abrasive grains attached to each small abrasive-grain-layer part more than that of central domain.
The other aspect of the abrasive tool concerning to the present invention, is characterized by arranging several small abrasive-grain-layer parts, which have the opening for discharging grinding liquid, and forming them approximately in the center.
Since the openings are prepared approximately in the center of a small abrasive-grain-layer part, and supplies grinding liquid to the ultra abrasive grain of the circumference, it can be able to supply grinding liquid directly to the grinding point at the ultra abrasive grain. Then, various grinding wastes are discharged without deposition or accumulations among ultra abrasive grains, and the viscosity of the grinding liquid mixed with the grinding waste is reduced, and discharged smoothly. Furthermore, it can promote cooling of ultra abrasive grains and can also lessen damage.
Moreover, the discharge way may be formed at other domain different from small abrasive-grain-layer parts (protruded part). On both sides of the grinding point at the small abrasive-grain-layer parts, the source of supply and discharge way of grinding liquid are laid out, and distance of them can be shortened as much as possible. Then grinding liquid spreads around at grinding point sufficiently, and prevents to accumulate grinding wastes on ultra abrasive grains, and wash away them smoothly.
Moreover, the diameter of the opening at small abrasive-grain-layer parts may be in the range xcfx860.5-3.0 mm. If the diameter (d) of the opening is smaller than 0.5 mm, grinding liquid cannot be supplied sufficiently to grinding point. And if it exceeds 3.0 mm it is not desirable, since the existence ratio of small abrasive-grain-layer parts will decrease and grinding capability will decline.
Moreover, the diameter (D) of protruded parts may be 2 to 10 times larger than the diameter (d) of an opening. Then it is possible to prevent deposition of the grinding waste at grinding points and to wash them away smoothly within this limit.
The range of the height of the protruded parts to base metal may be within 0.1-5.0 mm. Grinding liquid and grinding wastes are poured and discharged easily between the discharge ways at base metal and grinding points, if they are within this range.
The range of the distance between adjacent protruded parts (L) may be ⅓xcx9c2 time of the mean outer diameter (D) of protruded parts. If it is within this range, the interval of small abrasive-grain-layer parts can be set up pertinently, the abutment pressure of ultra abrasive grains can be maintained at high value, and moreover various grinding wastes can be smoothly discharged with grinding liquid through this gap.
The abrasive grain layer may be formed in the shape of a ring with two or more layers, or in the shape of spiral. Then, the sum of the grinding length of each abrasive grain layer, in the direction almost parallel to the relative movement direction of a grinding work piece, can be made almost uniform at arbitrary position of the direction which intersects almost perpendicularly in the movement direction of grinding work piece. Moreover, if an abrasive grain layer is constituted from three or more layers, the sum of the area of the abrasive-grain-layer domain in the arbitrary position, which intersects perpendicularly in the direction almost parallel to the relative movement direction of a grinding work piece, can be easily made into uniform.
The discharge path may be formed among the abrasive grain layers of two or more layers in the direction of a diameter at intervals. The discharge path may consist of the sub-discharge path formed among the small abrasive-grain-layer parts adjoined each other, and also of main discharge path formed among the plural abrasive grain layers, which are in the shape of a ring or spiral, adjoined each other in the direction of diameter. Various kinds of grinding wastes produced by the grinding in a small abrasive-grain-layer parts are washed away with the grinding liquid supplied from the opening at small abrasive-grain-layer parts, and flows along sub-discharge path. And discharged outside through the main discharge path. Then grinding wastes are discharge easily, and suppress carrying deposition and accumulation among ultra abrasive grains.
Moreover, a single layer of ultra abrasive grains may be adhered to the metal binder phase of the small abrasive-grain-layer part toward the thickness direction, and called as a single layer abrasive tool.
According to the present invention, the abrasive tool with metal binder phase may possess the first small abrasive-grain-layer parts and the second small abrasive-grain-layer parts. The first small abrasive-grain-layer parts incline one directionally against the central line toward the direction of a diameter, and the second small abrasive-grain-layer parts incline to the opposite direction against the first small abrasive-grain-layer parts mentioned above.
Because the first and the second small abrasive-grain-layer parts are prolonged and laid out mostly toward the direction of the center of base metal, the stability of the grinding tool is improved at the time of grinding. The contact surface and contact pressure to the grinding work piece are also stabilized, then minute vibration etc. is suppressed, and grinding work piece is not damaged even at partial area. Furthermore, the first and second small abrasive-grain-layer parts are inclined toward the central line in right and opposite direction respectively, clogging are canceled and fall of sharpness can be prevented in such way. That, considering the relative movement between the grinding work piece and above-mentioned abrasive tools, for example, grinding length of the first small abrasive-grain-layer parts are long and tend to carry out clogging, on the other hand the second abrasive-grain-layer parts have short grinding length.
Therefore, clogging and cancellation of clogging will be performed at micro regions, then the minute vibration at the time of grinding can be suppressed.
Moreover, the first and second small abrasive-grain-layer parts may be different in aspect ratio respectively. Stability is improved, and if an aspect ratio is small, the capability of clogging cancellation will be improved. Moreover, small abrasive-grain-layer parts may be dissociated mutually, and mostly in rhombic shape, and may be arranged in radiation pattern.
Moreover, the first and second small abrasive-grain-layer parts are arranged in the direction of a circumference of base metal in turn, and the abrasive grain layer may be making the shape of a ring. Considering relative movement between the grinding work piece, one of the first and second small abrasive-grain-layer parts may cause clogging because of long grinding length, another can cancel clogging since grinding length is short, then the fall of sharpness can be prevented. Performing clogging and cancellation of clogging in turn at the time of grinding, the minute vibration at the time of grinding can be suppressed, then good sharpness can be maintained.
Small abrasive-grain-layer parts have the portion with one-directionally inclined toward the central line of the direction of diameter passing through the center of a base metal, and the portions which inclines to an opposite direction. Stability at the time of grinding is improved, and minute vibration etc. are suppressed, and moreover, one of small abrasive-grain-layer parts tends to carry out clogging with long grinding length and other with short grinding length cancel clogging, then fall of sharpness are prevented.
Moreover, the small abrasive-grain-layer parts may contain the third small abrasive-grain-layer parts and the fourth smallness abrasive-grain-layer parts, that are formed in the shape of curve and countered on both sides of a central line, faced both sides, or slipped each other along with central line.
The small abrasive-grain-layer parts may be arranged all over the base metal, and can promote increase the amount of grinding much more and also cancellation of clogging.
The other aspect of the electrodeposit abrasive tool at the present invention, small abrasive-grain-layer parts are characterized by a single ultra abrasive grain adhered at the metal binder phase.
Since each ultra abrasive grain is adhered singly on each protruded part, grinding wastes and slurry etc. are not blocked and deposited among ultra abrasive grains, and do not becomes sticky waste, then discharged smoothly.
Furthermore, even if a grinding work piece was elastic like the pad of CMP equipment, whole surface contact doesn""t occur and only the single ultra abrasive grain at small abrasive-grain-layer parts carries out grinding.
Therefore, abutment pressure is maintained at high value, sharpness is good, and the discharge performance of grinding wastes is also good.
Moreover, ultra abrasive grain may be adhered at the small abrasive-grain-layer parts formed at the concave parts at the upper surface of the protruded parts of a base metal. If ultra abrasive grains are laid and adhered by electroplate etc. at the concave part of protruded parts on manufacturing of an abrasive tool, then positioning of ultra abrasive grains are easy, and it can be projected and laid so that the corner part of the crystal object of an ultra abrasive grain may turn toward upper part tip. Therefore, grinding performances, such as grinding accuracy and grinding efficiency, are high.
Moreover, the outer diameter (D) of protruded parts may be 1.3 to 3 times as much range as the mean particle diameter of an ultra abrasive grain. Within this limit, it is possible to prevent deposition of the grinding wastes at a grinding point, and to wash them away smoothly. If smaller than 1.3 times, the intensity of protruded parts is weak and ultra abrasive grains will drop out easily by grinding resistance and protruded parts will break easily. If larger than 3 times, the arrangement interval of an ultra abrasive grain becomes too large, and grinding capability will decline or a fault, such as promoting wear of ultra abrasive grains, will arise.
Moreover, the range of the height (H) of the protruded parts to a base metal may be within 0.05-3.0 mm. Within this range, grinding liquid and grinding wastes are poured easily and can be discharged between grinding point and the discharge path on a base metal.
An electrodeposited abrasive tool concerning the present invention characterized by blocky ultra abrasive grains.
Although the sharpness of the ultra abrasive grains with blocky shape is inferior compared with the ultra abrasive grains with irregular shape. Since the blocky ultra abrasive grains have the shape of regular polygons, such as a right hexagon, which the corner part has seldom jutted out, or the shape near form sphere, corner part or ridgeline part, etc. are seldom crushed or drop out, and seldom produces the fragment by crush etc. Moreover it doesn""t cut too much at the time of grinding, then seldom produces a scratch at grinding work piece.
Furthermore, even if ultra abrasive grains were blocky, ultra abrasive grains are singly and was mutually distributed, and the small abrasive-grain-layer parts, where plural blocky ultra abrasive grains are gathered and adhered by the metal binder phase, are laid out and distributed mutually. Then the absolute number of an ultra abrasive grain is reduced, and cutting performance and sharpness of a corner part are kept in good condition, if a single ultra abrasive grain is attached at each small abrasive-grain-layer part. Moreover, cutting in and cutting performance are rather good and grinding performance is kept in good condition, because grinding is performed at the ridgeline of the array of ultra abrasive grains around perimeter area, if the ultra abrasive grains are gathered.
Moreover, plural ultra abrasive grains adhere to the small abrasive-grain-layer part, and blocky ultra abrasive grains may be laid out at the perimeter.
Although sharpness is bad at the inside domain of blocky ultra abrasive grains because of the relation with other abrasive grains, grinding machining toward grinding work piece can be carried out in good condition, since the cutting in and sharpness is rather good at the corner part and a ridgeline part at the perimeter side without other abrasive grains. The ultra abrasive grain prepared at each small abrasive-grain-layer parts may be made into 1-500 pieces, and the ratio of the ultra abrasive grains to the whole surface product of the above-mentioned abrasive grain layer accounted by plane projection may be set as 2%-80% of the range.
Moreover, an electrodeposited abrasive tool concerning to this invention may be CMP conditioner.